Heat exchange device



Jan. 11, 1966 R. L. GARWIN HEAT EXCHANGE DEVICE Filed Nov. 18, 1963 N QEI NVENTOR RICHARD L. GARWiN MEDQHUE ATTORNEY United States Patent3,228,460 HEAT EXCHANGE DEVICE Richard L. Garwin, Scarsdale, N.Y.,assignor to Internationai Business Machines Corporation, New York, N.Y.,a corporation of New York Filed Nov. 18, 1963, Ser. No. 324,262 8Claims. (Cl. 16581) This invention relates to heat transfer devices andmore particularly to counter-flow heat exchangers for use in systemswhich provide extremely low temperatures for cryogenic devices and thelike.

Heat exchangers are utilized in practically every type of refrigerationand gas liquefying system, and their use and operation is well known inthese arts. Recently, however, due to the increased use of liquefiedgases as fuel for liquid-fueled rockets and as a coolant for cryogenicdevices, such as maser amplifiers which operate at temperature nearabsolute zero, refrigeration systems capable of producing lowtemperature liquids or of maintaining low temperatures have become moreand more important. Indeed, the investigation of low temperatures andtheir effects has become the intensively studied area of cryogenics, thebasic tools of which are systems capable of porducing low temperatures.

In the past, refrigeration equipment utilized to provide the liquefiedgases at the required low temperatures was bulky and expensive andincapable of long periods of uninterrupted operation. Now, however, dueto the relatively wide acceptance and utility of such systems, factorssuch as size, cost, reliability, and ease of assembly must be taken intoconsideration. Thus, an effort is being made to reduce structuralcomplexity and assembly time in important refrigeration systemcomponents such as heat exchangers.

Prior art heat exchangers, while they have performed their functionefliciently, have not been noted for their structural simplicity or caseof assembly. Complex structure, of course, leads to difiiculty inassembly which in turn contributes to high production cost andrelatively low reliability in operation. Difliculties have beenencountered principally in mounting heat transfer elements within theheat exchanger and, in preventing leakage between the fluid channels ofthe heat exchanger. Problems have also arisen in matching temperaturecoefiicients of expansion of the various materials required and inmaintaining solder joints and seals under extremely low temperatureconditions. It appears, therefore, that a need exists for a heatexchanger which has simplicity of design, ease of assembly, relativelylow cost and high reliability, in addition to good efficiency.

It is therefore an object of this invention to provide a counter-flowheat exchanger which is an improvement over prior art heat exchangers.

Another object is to provide a heat exchanger which is compact,relatively easy to assemble and low in cost.

A further object is to provide a heat exchanger which is operable andreliable at extremely low temperatures.

A feature of this invention is the utilization of means defining firstand second fluid flow paths and heat transfer elements common to saidpaths to transfer heat therebetween.

Another feature of this invention is the utilization of a plurality ofhigh heat conductivity heat-transfer elements which have a plurality ofperforations therein, and, a plurality of relatively low heatconductivity spaceror blocking-elements which are interposed between theheat transfer elements. The spacer or blocking elements separate theheat transfer elements and simultaneously block certain ones of theperforations in the heat transfer elements so that at least two fluidflow channels are formed within Patented Jan. 11, 1966 a heat exchangercasing. In this fashion, uninterrupted paths of high-conductivity metalcarry the heat from one stream to the other.

A further feature of this invention is the utilization of resilientretaining means which apply a compressive force to the heat transfer andblocking elements so that, regardless of the expansion and contractionencountered due to temperature changes, the axial position of theelements is controlled and the elements are held tightly together toprevent fluid leakage between channels.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawings.

In the drawings:

FIG. 1 is a longitudinal partially cut away cross-sectional view of thecounter flow heat exchanger according to this invention and,

FIG. 2 is a cross-sectional view of the heat exchanger taken along lines22 of FIG, 1 which shows the juxtaposition of heat transfer elements andspacer elements within the casing of the heat exchanger.

A counterflow heat exchanger is a device which takes advantage of therecirculation of a low temperature fluid which has been utilizedpreviously to maintain some component such as a maser at a given lowtemperature. The recirculated low temperature fluid is utilized topre-cool incoming fluid at a relatively high temperature to a lowertemperature by transfer of heat in the heat exchanger by some heattransfer means. The transverse flow of heat from stream to stream isfacilitated, and the flow of heat along the heat exchanger is impeded asmuch as possible, for best efliciency. In this manner, extremely lowtemperatures are achieved relatively quickly and the efiiciency of therefrigeration system is enhanced. In the usual refrigeration system,several heat exchangers may be utilized to obtain heat transfer atseveral different points in the system.

T o simplify the following description, Where portions of the heatexchanger of this invention correspond to other portions, the samereference number will be utilized, it being understood that the inputand output sections of the heat exchanger are structurally identical.

Referring now to FIG. 1, there is shown a counter-flow heat exchanger 1having an outer casing 2 of relatively low heat conductivity materialsuch as stainless steel. Heat exchanger casing 2 forms the boundary of afirst fluid flow path or channel through which, in the usual case, arelatively low temperature, low pressure fluid is recirculated afterhaving cooled some component, such as a maser, at a point, not shown,beyond heat exchanger 1, The first fluid flow path or channel is showngenerally at 3 in FIG. 1. A second fluid flow path or channel, showngenerally at 4, is disposed internally of and coaxially of the firstfluid flow path or channel 3. The second fluid flow path or channel 4 ispartially defined by inflow and outflow tubulation 5 and by an enlargedresilient portion 6 thereof, both preferably having a circularcross-section. Tubulation 5, made preferably of stainless steel extendsinto casing 2 through a circular aperture 7 in cup-shaped end piece 8,the outer surface of which fits tightly against a portion of the innersurface of casing 2. A flange 9 on the extremity of end piece 8 engagesthe extremity of easing 2 to limit the distance of insertion of endpiece 8 into casing 2. A counter sunk portion 10 about circular aperture7 is adapted to receive the end of a cylindrical sleeve 11 which isreceivable on tubulation 5. Sleeve 11, preferably of stainless steel, issoldered at an end 12 to tubulation 5, and, flange 9 is soldered to theextremity of easing 2. In this manner, axial movement of tubulation 5and resilient portion 6 is prevented and a compressive force is exertedby resilient portion 6 in a manner to be more fully describedhereinafter.

In FIG. 1, a plurality of annular spacer or blocking elements 13,preferably made of nylon or other low heat conductivity material, isshown disposed internally of a portion of easing 2, the annular spaceror blocking elements 13 defining another portion of the second fluidflow path or channel 4. Also disposed internally of casing 2 is aplurality heat transfer elements 14 of high heat conductivity materialsuch as copper or other suitable material. Elements 14 are of circularcross section (see FIG. 2) and are interposed periodically betweenspacer or blocking elements 13 along the length of casing 2.

FIG. 2 shows clearly the juxtaposition of spacer or blocking elements 13and heat transfer elements 14 within casing 2. Spacer or blockingelements 13 are contiguous with the surface of heat transfer elements 14over a minor portion which divides elements 14 into major portions 16and 17. Thus, major portions 16 and 17 are interposed in first andsecond flow paths 3 and 4, respectively. It should be noted that heattransfer elements 14 are common to both first and second flow paths 3, 4and that fluid flow through paths 3, 4 is made possible by virtue of aplurality of perforations 18 which extend through each of the heattransfer elements 14 and permit the passage of fluid through majorportions 16 and 17. Spacer or blocking elements 13, act to space apartheat transfer elements 14 so that lateral rather than longitudinaltransfer of heat between fluids is accomplished and block certain onesof perforations 18 to prevent passage of fluid therethrough. By virtueof the arrangement of heat transfer elements 14 and blocking elements13, a portion of second fluid flow path 4 is formed which consists ofthe annular blocking elements 13 and minor portions 15 of heat transferelements 14. Reference numeral 15, while directed to annular blockingelement 13, is intended to define a minor portion of heat transferelement 14. The minor portion 15, therefore, is that portion of element14 which is in registry with blocking element 13. It should be clearthat perforations 18 which are in registry with annular blocking element13 transmit no fluid and accordingly act as a portion or boundary ofsecond flow path or channel 4.

Referring again to FIG. 1, it may be seen that enlarged resilientportion 6 of tubulation 5 has a radially extending portion 19 which isbent at a small acute angle from the vertical. Also, resilient portion 6has an extremity extending radially inwardly which is also bent at asmall acute angle with respect to the vertical. The angular displacementof portion 19 and extremity 20 is due to the positioning of extremity 20against the first and last of the plurality of blocking elements 13 suchthat a compressive force is applied to elements 13 and maintainedthereon by soldering cylindrical sleeve 11 at its end 12 to tubulation5. The compressive force acts on blocking elements 13 and heat transferelements 14 so that the intervening wall formed by the elements 13 andminor portion 15 of heat transfer elements 14 is substantially fluidtight even though contraction of elements 13 and 14 takes place whencontacted by the low temperature fluids. Using the foregoing technique,the axial movement of elements 13 and 14 is controlled and asubstantially fluid-tight wall is maintained intermediate the majorportions 15, 16 of heat transfer elements 14. Referring again to FIG. 2,it may be seen that perforated heat transfer elements 14 completely fillcasing 2. Elements 14 are not, however, attached to the inner surface ofcasing 2, but rather are in slidably engaging relationship therewith sothat elements 14 can freely move when expansion and contraction due totemperature changes takes place. Spacer or blocking elements 13 must bemaintained within casing 2 in a given radial position and this isaccomplished by providing radially extending fingers or protuberances 21which, like heat transfer elements 14, are in slidably engagingrelationship with the inner surface of casing 2. In connection with theuse of spacer or blocking elements 13, only the formation of two flowpaths or channels has been indicated within casing 2. There is, however,no reason why a number of concentric spacer or blocking elements couldnot be provided to form three or more flows paths or channels within aheat exchanger casing. Under such circumstances, appropriate inflow andoutflow tubulation would have to be provided for each of the resultingchannels. It is also possible to solder, connect, or otherwise aflix thespacer elements 13 to the heat-transfer elements 14, providing agas-tight connection by means of a bellows or spring enclosure like theend-piece 19 and 20. Copperclad phenolic spacers have been successfullyutilized.

In FIG. 1, inflow and outflow tabulation 22 is soldered intoexcentrically displaced circular aperture 23 to carry recirculated lowpressure fluid to and from first fluid flow path 3.

A successful operating model of heat exchanger 1 was constructed havingthe following dimensions:

Overall length 4.25 inches. Casing diameter 1.05 inches.

Casing thickness 16 mils.

Heat Transfer element diameter 1.469 inches.

Heat Transfer element thickness 15 mils.

Spacer diameter 1.03 1 inches. Spacer thickness 30 mils. Perforations 15mil diameter on 30 mil centers.

Heat exchanger 1 may be assembled by soldering a pre-assembled portionconsisting of tubulation 5 and 22 and end pieces 8 to casing 2 at flange9. Blocking or spacer elements 13 and heat transfer elements may then bestacked alternately until a total of fifty-five spacer elements 13 andfifty-four heat exchange elements 14 are disposed within casing 2. Atthis point, a second preassembled portion identical to that referred toabove is inserted and soldered to complete the assembly of heatexchanger 1.

From the foregoing, it is clear that heat exchanger 1 may be assembledrelatively easily and that it consists of easily obtainable, relativelyinexpensive parts. The arrangement of the various parts requiring aminimum of soldering operations results in increased reliability as wellas minimizing the overall cost of such heat exchangers.

In operation, a high pressure stream of gas at 300 p.s.i. passes alongsecond fluid flow path 4 and heat is absorbed by a stream of lowpressure gas at 15 p.s.i. in first fluid flow path 3. The low pressurefluid is a gas which is being recirculated to heat exchanger 1 to coolan incoming gas to a temperature where expansion through aJoule-Thompson valve will cause the gas to liquefy.

While a counter-flow heat exchanger has been described herein as apreferred embodiment, it should be appreciated that the same structuremay be utilized as a heat transfer device in which the fluids flow inthe same direction. In such an arrangement, there would be a lateraltransfer of heat between the streams but no temperature differentialwould be apparent from one end of the heat exchanger to the other. Inthe counter flow type heat exchanger, while there is a similar lateraltransfer of heat, there is a temperature differential from one end ofthe heat exchanger to the other. Apart from the temperature differentialdue to flow direction, there is no diflerence in the operation orstructure of the heat exchanger for either type of flow.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is: 1. A heat exchanger for transferring heat betweenfluids at diflerent temperatures comprising:

means defining a first fluid flow path, means defining a second fluidflow path disposed coaxially of said first path and heat transferelements common to said first and second flow paths interposed in saidpaths to transfer heat therebetween, said means defining a second fiowpath including a plurality of discrete low heat, conductivity spacerelements disposed internally of and lengthwise of at least a portion ofsaid first fluid flow path and periodically interposed between saidheat-transfer elements and input and output tubulation having enlargedresilient transition portions, an extremity of each of said portionsbeing connected to a spacer element to apply a compressive force to saidspacer elements and said heat transfer elements to compensate fordimensional changes due to temperature variation to prevent fluidleakage between said first and second flow paths and to control theaxial movement of said spacer and heat transfer elements. 2. A heatexchanger for transferring heat between fluids at different temperaturescomprising:

means defining a first fluid fiow path, means defining a second fluidflow path disposed c0- axially of said first path, heat transferelements common to said first and second flow paths interposed in saidpaths to transfer heat between said first and second flow paths, saidmeans defining a second flow path including a plurality of discrete lowheat-conductivity spacer elements disposed internally of and lengthwiseof at least a portion of said first fluid flow path and periodicallyinterposed between said heat-transfer elements, and means formaintaining the radial positioning of said spacer elements including aplurality of protuberances integral with said elements and adapted toslidably engage said means defining a first flow path. 3. In a heatexchanger for transferring heat between fluids at different temperatureshaving a low heat conductivity casing:

heat transfer means comprising a plurality of heat conductive elementshaving a plurality of perforations therein to permit the passage offluid therethrough disposed internally of said casing, means interposedbetween said elements to block the passage of fluid through certain onesof said perfora tions thereby forming at least two discrete channels forfluid flow within said casing,

and resilient retaining means adapted to position said conductiveelements and said blocking means within said casing to control the axialmovement of said elements and said blocking means and means integralwith said blocking means to position said blocking means within saidcasing to prevent radial movement thereof.

4. In a heat exchanger heat transfer means according to claim 3 whereinsaid blocking means includes an endless strip of low heat conductivitymaterial.

5. In a heat exchanger heat transfer means according to claim 3 whereinsaid blocking means includes an annulus of low heat conductivitymaterial.

6. In a heat exchanger heat transfer means according to claim 3 whereinsaid resilient retaining means comprises:

inflow and outflow tubulation for one of said channels each having aportion thereof rigidly fixed to said casing and an enlarged portionhaving an inwardly extending extremity connected to one of said blockingmeans adapted to maintain said conductive elements and said block-ingmeans in compression to provide at least two discrete channels theintervening wall of which is substantially fluid tight and compensatesfor dimensional variation due to changes in temperature.

7. In a heat exchanger heat transfer means according to claim 3 whereinsaid means integral with said blocking means to radially position saidblocking means comprises:

a plurality of protuberances extending radially from said blockingmeans, said protuberances being in slidably engaging relationship withsaid casing.

8. In a heat exchanger heat transfer means according to claim 3 furthercomprising:

inflow and outflow tubulation for at least another of said channelsfixedly connected to said casing.

References Cited by the Applicant UNITED STATES PATENTS 604,823 5/1898Forbes l179 1,724,351 8/1929 Henderson et al. 81 X 1,863,586 6/1932Wilke 165-135 2,451,629 10/1948 McCollum 165154 X 2,580,715 1/1952 Baber165-81 2,879,976 3/1959 Rose a- 165154 X FREDERICK L. MATTESON, 111.,Primary Examiner.

1. A HEAT EXCHANGER FOR TRANSFERRING HEAT BETWEEN FLUIDS AT DIFFERENTTEMPERATURE COMPRISING: MEANS DEFINING A FIRST FLUID FLOW PATH, MEANSDEFINING A SECOND FLUID FLOW PATH DISPOSED COAXIALLY OF SAID FIRST PATHAND HEAT TRANSFER ELEMENTS COMMON TO SAID FIRST AND SECOND FLOW PATHSINTERPOSED IN SAID PATHS TO TRANSFER HEAT THEREBETWEEN, SAID MEANSDEFINING A SECOND FLOW PATH INCLUDING A PLURALITY OF DISCRETE LOW HEAT,CONDUCTIVITY SPACER ELEMENTS DISPOSED INTERNALLY OF AND LENGTHWISE OF ATLEAST A PORTION OF SAID FIRST FLUID FLOW PATH AND PERIODICALLYINTERPOSED BETWEEN SAID HEAT-TRANSFER ELEMENTS AND INPUT AND OUTPUTTUBULATION HAVING ENLARGED RESILIENT TRANSITION PORTIONS, AN EXTREMITYOF EACH OF SAID PORTIONS BEING CONNECTED TO A SPACER ELEMENT TO APPLY ACOMPRESSIVE FORCE TO SAID SPACER ELEMENTS AND SAID HEAT TRANSFERELEMENTS TO COMPENSATE FOR DIMENSIONAL CHANGES DUE TO TEMPERATUREVARIATION TO PREVENT FLUID LEAKAGE BETWEEN SAID FIRST AND SECOND FLOWPATHS AND TO CONTROL THE AXIAL MOVEMENT OF SAID SPACER AND HEAT TRANSFERELEMENTS.